The primary goal is to support Projects 1, 2 and 3 by supplying precise and accurate measurements of markers of bone formation and bone resorption, serum levels of calcium-regulating hormones, and of structural variables in the upper femora. Bone formation will be assessed by serum osteocalcium and serum bone alkaline phosphatase. Bone resorption will be assessed by urinary n- telopeptide crosslinks. Calcium-regulating hormones will be assessed by serum parathyroid hormones, serum 25OH vitamin D, and serum 1,25(OH)2 vitamin D. Health and safety will be assessed by a hematological and biochemical screen and pregnancy tests. Bone structure at the hip will be measured from radiographs and from volumetric quantitative computed tomography scans. The core will also be responsible for ensuring: that all biological samples and radiological images arising from Projects 1, 2 and 3 are logged-in, processed and stored under optimal conditions; that assays and structural variables are performed with precision and accuracy; that the data generated are entered in appropriate databases and transferred in a timely fashion to the Administrative and Biostatistics Core (Core A) and the Informatics and Genetics Core (Core C) for analysis.